The FB engines were manufactured at Subaru’s Gunma Oizumi factory which was developed exclusively for the production of the FB engine. The FB20 engine had an open-deck, aluminium cherry cordial little debbie block with 84. 0 mm bores and a 90. FB20 engine had cast iron liners.
Due to its revised connecting rods and valvetrain components, the FB20 block was the same size as its EJ204 predecessor, despite its smaller bore and longer stroke. According to Subaru, the longer stroke improved fuel efficiency by enabling faster air induction and reduced unburnt fuel during cold starts. The FB20 engine had separate cooling circuits for the cylinder block and head to improve coolant distribution. Around the block, the flow rate was limited to maintain a high temperature for the cylinder liner oil, thereby reducing friction from the motion of the pistons.
To reduce engine width and enable its longer stroke, the FB20 engine had asymmetrical, diagonally-split connecting rods. Compared to its EJ predecessor, the FB20 engine achieved an approximate 30 per cent reduction in frictional losses due to its lighter connecting rods, lighter pistons and wrist pins, and lower piston-ring tension. Furthermore, the size and shape of the resonators in the intake manifold were streamlined. The FB20 engine had an aluminium alloy cylinder head with separately cast camshaft carriers so that cores in the cylinder head could be omitted for a reduction in metal thickness.
As noted above, cylinder head cooling was enhanced by using separate circuits for the cylinder block and head. The FB20 engine had double overhead camshafts that were driven by a maintenance-free chain. For the FB20 engine, a chain drive was adopted because it enabled a narrower included valve angle and a reduction in the sprocket diameters of the crank and camshaft for reduced width. Whereas the fuel injectors for the EJ204 engine were in the intake manifold, the fuel injectors for the FB20 engine were moved to the cylinder head. According to Subaru, positioning the injectors in the cylinder head enhanced the flow of atomised fuel, thereby improving fuel efficiency and reducing exhaust gas emissions. The FB20 engine had coil-on-plug ignition with an integrated igniter for each cylinder. The spark plug caps, which provided contact to the spark plugs, were integrated with the ignition coil assembly.
For the FB20 engine, cooling around the spark plugs was improved for a higher knock limit, increased power and improved fuel efficiency. For the FB20 engine, the diameters and lengths of the exhaust manifold were modified to improve catalytic converter warm-up and increase power output. Furthermore, the more free-flowing exhaust system contributed to higher power output. By using EGR, combustion temperatures were reduced such that the engine was less susceptible to knock and injection timing could be advanced.
Reviews is an independent publisher of car reviews, recalls, faults, image galleries, brochures, specifications and videos. Subaru’s EJ257 was a turbocharged, 2. The EJ257 engine had a die-cast aluminium block with 99. 5 mm bores and a 79. 0 mm stroke for a capacity of 2457 cc. The EJ257 engine had a semi-closed deck design whereby the cylinder walls were attached to the black at the twelve, three, six and nine o’clock positions. For the EJ257 engine, the crankshaft was supported by five main bearings and, like other EJ Phase II engines, the crankshaft thrust bearing was positioned at the rear of the crankshaft.
The connecting rods were made from forged high carbon steel, while big end cap dowel pins and set screws were used for accurate mating. The EJ257 engine had cast aluminium pistons with an Alumite coating for the piston head and ring grooves, and a molybdenum coating for the piston skirts. The EJ257 engine had a die-cast aluminium cylinder head that was mounted on a head gasket which consisted of three stainless steel sheet layers. The single timing belt had round profile teeth for quiet operation and was made from a strong flexible core wire, wear resistant canvas and heat resistant rubber.